Rivet setting tool for blind rivets

ABSTRACT

A rivet setting tool for blind rivets is disclosed which, in construction, includes gripping means for grasping the mandrel of a blind rivet and pulling means coacting with the gripping means for retracting the gripping means to pull the mandrel into the eyelet of the rivet to set same. The tool also includes specially constructed spring means cooperatively engaging the gripping and pulling means which operates to automatically initiate retraction of the pulling means to move the gripping means into contact with the mandrel under a relatively light pressure sufficient to hold the rivet in place relative to the tool. The tool further includes means for actuating the gripping and pulling means which includes a pivotally mounted handle supported by specially constructed means reducing wear and tear on the support structure. A special wear-resistant insert for the nose piece of the tool is also disclosed.

United. States Patent 11 1 Di Maio RIVET SETTING TOOL FOR BLIND RIVETS [75] Inventor: Anthony E. Di Maio, Georgetown,

Mass.

[73] Assignee: Marson Corporation, Chelsea, Mass.

[ Oct. 22, 1974 Primary Examiner-Charles W. Lanham Assistant Examiner-Gene P. Crosby [57] ABSTRACT A rivet setting tool for blind rivets is disclosed which, in construction, includes gripping means for grasping the mandrel of a blind rivet and pulling means coacting with the gripping means for retracting the gripping means to pull the mandrel into the eyelet of the rivet to set same. The tool also includes specially constructed spring means cooperatively engaging the gripping and pulling means which operates to automatically initiate retraction of the pulling means to move the gripping means into contact with the mandrel under a relatively light pressure sufficient to hold the rivet in place relative to the tool. The tool further includes means for actuating the gripping and pulling means which includes a pivotally mounted handle supported by specially constructed means reducing wear and tear on the support structure. A special wearresistant insert for the nose piece of the tool is also disclosed.

12 Claims, 10 Drawing Figures [22] Filed: Jan. 29, 1971 [21 Appl. No.: 110,912

[52] US. Cl. 72/391 [51] Int. Cl. B2lj 15/38 [58] Field of Search 72/391, 114, 453

[5 6] References Cited UNITED STATES PATENTS 3,302,444 2/1967 Elliott 72/391 3,324,700 6/1967 Elliott 72/391 3,328,985 7/1967 Keymer.... 72/391 3,376,727 4/1968 Hinden 72/391 3,491,578 1/1970 Biermann 72/391 3,548,627 12/1970 Henshaw 72/391 3,561,249 2/1971 Freeman 72/391 3,646,800 3/1972 Martin 72/391 FOREIGN PATENTS OR APPLICATIONS 1,116,324 l/l956 France 72/391 Email! 57 E1551 i I Pmmwwzz 3.842.649

INVENTOR. ANTHONY E. DIMAIO ATTOR N E Y PAIENTEU W 3.842.649 MET 20$ 4 mmqmgr & 1 ,0329);

INVENTOR.

ANTHONY E DIMAIQY BY ATTORNEY PAFENIEBumzmm 1842.649 2 so; a

ANTHONY EDIMAIO BY ATTORNEY RIVET SETTING TOOL FOR BLIND RIVETS BACKGROUND AND SUMMARY OF THE INVENTION tubular eyelet with a pre-formed flange mounted on one end and an elongated mandrel slidably disposed within the bore of the eyelet in close fitting relation-. ship. The mandrel has a head at one end which externally abuts the non-flanged end of the eyelet. The other end of the mandrel projects outward of the eyelet beyond it flanged end. To fasten work pieces together, say two metal plates, the rivet is inserted into registering holes in the plates so that the preformed flange abuts the accessible side of the plates with the eyelet extending through both plates such that its non-flanged end projects beyond the blind or inaccessible side of the plates. The holes in the plates are sized to receive the eyelet by a slip fit. The rivet is set by applying a pulling force to the projecting portion of the mandrel relative to the eyelet thereby drawing the enlarged end of the mandrel into the eyelet. This produces an outward flaring or deformation of the eyelet; the flaring advancing into an opening within the confined spaces. This is an ext-emely advantageous result.

In the tool of this invention, the driving portion is offset from the handles. While conventional driving portions are made relatively short, the driving portion of the tool of this invention has a length of at least onefifth of the length of the tool. As a result, a rivet can be set in a deep channel by using the tool as a rivet carrier which is very advantageous.

In tools of the type involved in this invention it is necessary to pivot the handle of the lever arm to the body.

progressively along the eyelet as the enlarged end of the mandrel is forced through the eyelet. Eventually the metal plates are clamped tightly together between the pre-formed flange and the flange-like flare. The tensile strength of the mandrel is eventually exceeded and the mandrel breaks off at a predetermined point which generally lies substantially flush with the preformed flange of the eyelet thus leaving the metal plates fastened together by a neat and strong riveted bond.

The conventional rivet setting tool for this type of blind rivet generally includes gripping means comprising, typically, a pair of co-acting jaws which grip the mandrel and which exert a pulling force on the mandrel to set the rivet as above described. The tool-also includes actuating means for operating the jaws. The actuating means typically comprises a lever arm generally incorporated. in a handle which constitutes the force application element for operating the jaws. With prior art constructions, the handle is normally biased in open position with a second fixed handle in spaced relationship therewith. Thus the jaws are also biased in the open position. The jaws are moved to the closed or operable position by squeezing the handles together. This compression of the handles causes the jaws to compress against the mandrel and pull the same.

When rivet setting tools having the handles and thus the jaws biased in open position are inadvertently released prior to the full completion of the stroke or where a second stroke is required to properly set the rivet, the jaws will open and will release the mandrel. This is generally not a desirable thing. In the present invention, according to the presently preferred embodiment, spring means are provided which bias the handles in closed position. This means that inadvertent release of the handles will not open the jaws from their compressed position about the mandrel and the rivet will not fall out of the tool. This further means that the tool can actually be used as a rivet inserter, particularly within confined spaces, by opening the handles, placing the mandrel within the open jaws, releasing the handles to compress the jaws about the mandrel and then placing the rivet portion, which is now secured to the tool,

This pivoting has in the past been accomplished by means of a pin having an enlarged head and a projecting shank both of which are circular in cross-section. The head of the pin is generally supported in a circular opening in one side of the body and the terminal portion of the shank is similarly supported in a circular opening in-the opposite side of the body. The terminal ends of the pin generally project outward beyond the respective sides of the body by a small but significant distance. This is, of course, quite disadvantageous because the tool can snag or catch on the clothing of the operator, on buttons, on projections, etc. In the tool of this invention a first upstanding boss is provided to substantially surround the head of the pin and a second upstanding boss is provided to substantially surround the projecting terminal portion of the shank of the pin to the level of the end securing means. Thus the problem of snagging is either avoided or greatly minimized.

Supporting the pivot pin in the manner taught by prior art constructions has also proved undesirable in certain instances primarily because such an arrangement offers insufficient resistance to wear and tear. After extended use of the tool the openings in the body supporting the pin, or the pin itself, may tend to be-' come deformed resulting in a loose uneven fit of the pin. This, in turn, produces uneven and jerky operation of the handles which can interfere with proper tool operation and may ultimately lead to complete breakdown of the tool. The present invention also includes a relatively simple but specially constructed support structure for the pivot pin which provides improved wear characteristics.

Since the handles of the tool of this invention are biased in closed position means must be provided for the operator to easily open the jaws and selectively to hold them open. Since one hand of the operator of this invention will at one time be occupied in placing the mandrel of the rivet within the open jaws it is necessary to provide some type of auxiliary means to aid in opening these jaws. These means, in this invention, comprise a thumb rest portion which laterally projects from the body of the tool adjacent the handles.

Other objects and advantages of this invention, such as the specially constructed nose piece wear insert of the tool, will become apparent to the reader of this specification as the description proceeds.

The invention will be further described by reference to the accompanying drawings which are made a part of this specification.

FIG. 1 is a side elevational view of a rivet setting tool made in accordance with this invention showing the normal closed biased position of the handle members thereof.

FIG. 2 is a side elevational view of the type of blind rivet utilized in connection with the rivet setting tool of this invention.

in the position shown in FIG. 1.

FIG. 4 is a view similar to that of FIG. 3 but with the handle means pulled into open position showing the position of the parts in that condition.

FIG. 5 is a plan view of the rivet setting tool of this invention.

FIG. 6 is a fragmentary side elevational view of the rivet setting tool of this invention with the jaws in open position but biased toward the closed position and further showing the manner in which the mandrel is automatically gripped by the jaws of the rivet setting tool used as a rivet carrier to place a rivet within an opening located within a deep channel.

FIG. 7 is a fragmentary cross-sectional view taken along lines 77 of FIG. 1.

FIG. 8 is a fragmentary side elevational view essentially similar to the view of the tool depicted in FIG. 6 but showing the opposite side of the tool of this invention.

FIG. 9 is a fragmentary sectional view of the spring which biases the handles of the tool in closed position taken along lines 9-9 of FIG. 8.

FIG. 10 is a fragmentary cross-sectional view on an enlarged scale, showing a steel wear insert within the lower part of the offset driving portion of the tool of this invention.

The invention will now be further described by reference to the specific form shown thereof in the accompanying drawings. In this connection, however, the reader is cautioned to note that such specific form of this invention as described in the specification herein is for illustrative purposes and for purposes of example only. Various changes and modifications could obviously be made within the spirit and scope of this invention.

The rivet setting tool 11 of this invention includes a main body portion 12 and an offset housing 13 containing the driving portion of the tool-In the construction shown in the drawings driving portion 13 is cylindrical while body portion 12 includes a pair of spaced sides 14 and 15. Between sides 14 and 15 actuating means comprising, a handle 16 is pivotally connected by means of pin 17 which extends through mating openings located within sides 14 and 15 and handle 16. Pin 17 includes an enlarged head portion 18, a shank portion 19. In the construction shown the pin is supported at its headed end by a square holding portion 20 formed integrally with shank 19. The holding portion 20 is, in turn, supported in a mating square opening 21 is provided within side 14 of portion 12. The other end of pin 17 i.e., the terminal portion of shank 19) is supported by a square bushing member 23 disposed within a mating square opening 22 in side 15 of body 12. A washer 24 is mounted on the projecting end portion of shank 19.As shown the terminal end portion of shank 19 projects slightly outwardly of the external surface of side 15. To hold pin 17 in place a retainer in the form of a C-ring 25 is seated in a recess 26 provided in the projecting end portion of shank 19. A projecting boss 27 is provided on side 15 and surrounds the projecting end portion of shank 19 in substantially flush relationship to C-ring 25. A similarly situated projecting boss 28 is provided on side 14 in surrounding and substantially flush relationship to head 18 of the pin.

Handle 16 has a bifurcated end which defines two spaced actuator tenons having cam or bearing surfaces 29'. The tenons 29 are provided with openings 30 which are aligned with respect to each other and with respect to openings 21 and 22 in body sides 14 and 15, respectively, to receive pin shank 19 there through as best shown in FIG. 7.

Bifurcated tenons 29 are operatively connected to pulling member 32 in follower seats defined by a pair of oppositely disposed recesses 31 in pulling member 32. A longitudinal bore 56 is provided within portion 13 and pulling member 32 is adapted to move slidably within bore 56 in response to pivotal movement of handle 16 about pivot pin 17. Driving portion 13 is commonly made of a soft castable metal such as aluminum and a mild steel insert 52 is provided in the lower end of bore 56 for a purpose to be explained more fully below. Insert 52 has threads 53 therewithin and knurling 54 therewithout. Knurling 54 keeps insert 53 in position within bore 56 13 and threads 53 are adapted to mesh with mating threads 35 carried by removable nose piece 34. Nose piece 34 is provided with an bore 36 therewithin which is in alignment with bore 51 within upper jaw spreader 41 disposed within the lower portion of bore45 in pulling member 32. A mandrel 37 of a rivet 38 is adapted to be inserted into bores 36 and 51 with the eyelet portion 37a of rivet 38 positioned externally of the driving portion 13 below nose piece 34 as best shown in FIG. 7.

Mounted on the threaded portion of nose piece 34 is lower jaw spreader 39 which, as best seen in FIG. 10, includes a cone shaped cam surface 39'. Cam surface 39 coacts with the lower angled ends of jaws 40 to apply an opening force upon jaws 40 when jaws 40 are moved into contact therewith as will be more fully explained below. The opposite or upper ends of jaws 40 are subjected to a similar opening force when the similar cone shaped cam surface 41' on the .upper jaw spreader 41 is moved into contact with the upper angled ends of jaws 40 as will also be more fully explained below. Jaw spreader 41 has a reduced diameter shank portion 42 which is surrounded by coil spring 43. Coil spring 43 is disposed within bore in pulling member 32. The outer surfaces of jaws 40 taper inwardly toward their lower ends i.e. in the direction toward lower jaw spreader 39) and they contact internally disposed ta- I pering surface 44 in the lowermost portion of the lower part 57 of pulling member 32. Jaws 40 and tapering surface 44 are slidable relative to each other for a purpose explained more fully below.

Coil spring 43 is supported at its lower end on shoulder 43' of jaw spreader 41 and it is retained in bore 45 of pulling member 32 by a plug 46. As shown, plug 46 which is threadedly secured within the top portion of member 32, has a portion which fits within spring 43. A screw driver slot 47 is provided within plug 46 to permit this plug to be removed and inserted for assembly and disassembly purposes. Plug 46 is also provided with hole 58 which in conjunction with bores 45, S1 and 36 in pulling member 32, upper jaw spreader 41 and nose piece 34, respectively, provide a thrupassageway throughout the entire driving portion 13 of the tool, the purpose of which will be explained below.

A laterally projecting thumb rest 48 is carried by body 12 adjacent the handle portion. Knurling 49 is provided on thumb rest 48.

Nose piece 34 is designed to accommodate a mandrel of a rivet of a particular diameter. In the event another diameter of mandrel is to be employed in thetool or in the event the nose piece must be changed, provision is made for carrying a spare or alternate nose piece 34a located in a threaded hole in the tool as shown in FIG. 4.

With the foregoing specific description the operation of this invention will now be explained.

The operator of the tool grasps handle 16 and the corresponding handle portion of body 12 and, by holding his thumb of one hand on thumb rest 48, forces the handles apart with the other hand.

This movement will cause pulling member 32 to descend within bore 56 toward lower jaw spreader 39. During this downward movement jaws 40 are held by spring 43 in fully closed position as shown in FIG. 3. In their closed position it will be recognized that jaws 40 are wedged together by tapering surface 44 in the lower end of pulling member 32.

Continued movement of pulling member 32 will eventually bringthe angled ends 40' of jaws 40 into contact with cam surface 39' of jaw spreader 39 thus initiating upward movement of jaws 40 and jaw spreader 41 relative to pulling member 32 against the force of spring 43, now being compressed against plug 46 which is fixed relative to pulling member 32. During further downward movement of pulling member 32 in bore 56 with jaws 40 abutting stationery cam surface 39, the jaws are forced open at each end by the respective cam surfaces 39' and 40'. The jaws thus move laterally apart into substantially surface-to-surface contact with internal tapered surface 44. of pulling member 32, in which position they are fully opened as shown in FIG. 4. When fully opened, it will be recognized that jaws 40 are biased toward their closed position by spring 43; the handle 16 thereby being also biased toward its closed position (shown in FIG. 3) since the spring cooperatively engages the jaws and handle through jaw spreader 41. In other words, the handle 16 must be forcefully held fully opened to keep the jaws fully opened.

With the handle 16 and jaws 40 held fully opened, a rivet is inserted into the tool so that its mandrel extends into bores 36 and 51. The handle 16 is now released automatically initiating movement of pulling member 32 to move upwardly in bore 56 relative to jaws 40 in response to the force exerted against plug 46 by (now expanding) spring 43. In turn, jaws 40 are closed into contacting relationship with the mandrel under a relatively light pressure but sufficient enough to hold the rivet in the tool without pressure being exerted on the handle 16 by the operator. Now, using the tool as a carrier or holder for the rivet, the eyelet of the rivet is inserted through the work pieces to be fastened, as for example the channel 51 and plate 52 in FIG. 6.

After the rivet is in position the operator then squeezes the handles with considerable pressure and thus causing, in sequence, movement of jaws 40 into tight gripping relationship with mandrel 37 by reason of slight additional relative movement between pulling member 32 and jaws 40, and, movement of pulling member 32 and jaws 40, as a unit, upward in bore 56. Thereby, the mandrel is drawn or pulled through the eyelet as above described to set the rivet. As previously mentioned eventually mandrel 37 will break. The broken off part of mandrel is retained in the tool and is released by the operator by applying pressure to the handles to open them and again open the jaws. The broken off part of mandrel will fall through bore 36 by gravity if nose piece 34 is positioned downwardly or it will fall through the passageway defined by bore 51, 45 and 58 in jaw spreader 41, pulling member 32 and plug 46, respectively, previously mentioned, 58 by gravity if the tool is inverted by the operator.

The foregoing sets forth the manner in which the objects of this invention are achieved.

I claim:

1. In a rivet setting tool having a body, selectively operable actuating means, support means for pivotally mounting the actuating means on the body and rivet setting means within the body responsive to pivotal movement of the actuating means, the improvement wherein said support means comprises:

a. a pin-like element; and b. a member supporting the pin, saidmember having a polygonal-shaped bearing surface; and c. a polygonal-shaped surface carried by the body disposed in substantially surface-to-surface mating relationship with respect to said first mentioned polygonal shaped surface. 2. A rivet setting tool for blind rivets comprising, in combination, a body element having a main portion and an offset driving portion, a plurality of co-acting jaws disposed within said offset driving portion, actuating means controlling said jaws, an elongated handle pivotally connected to said body portion and operatively connected to said actuating means, a pin having a pair of end portions passing through said elongated handle and said body element, a boss carried by said body element adjacent each of the end portions of said pin, said pin having an enlarged head element and a square holding portion beneath said head, the portion of said body element adjacent said square holding portion provided with a matching square opening for receiving said holding portion.

3. A rivet setting tool as described in claim 2 wherein said body element is provided with an additional square opening laterally opposite said first named square opening and wherein a square holding element with a hole therethrough is disposed within said additional square opening.

4. A rivet setting tool as described in claim 3 wherein the portion of said pin adjacent said square holding element has retaining means thereupon.

5. A rivet setting tool as described in claim 4 wherein said retaining means comprises a washer member and a C-ring.

6. In a rivet setting tool for blind rivets having a body formed with a hollow driving portion made of a soft metal, a pair of co-acting jaws within said driving portion and a bored nose piece for receiving the mandrel disposed within a hole in said driving portion adjacent said jaws, the improvement which comprises a tubular insert of a hard metal disposed within said hole in intervening relationship to said nose piece and said driving portion.

7. A structure as described in claim 6 wherein said insert is made of mild carbon steel and said driving portion is made of aluminum.

8. A structure as described in claim 7 wherein the portion of said nose piece within said hole is externally threaded and wherein said insert has an outer surface and an inner surface with knurling upon said outer surface and threads on said inner surface.

9. In a rivet setting tool having a body, a handle member pivotally connected to said body, and rivet setting means operatively connected with said handle member, the improvement that comprises a pin pivotally connecting said handle member to said body, said pin having a polygonal portion disposed thereupon, said body having amating polygonal recess to accommodate said pin so that said pin will not turn during pivotal movement of said handle.

10. A structure as described in claim 9 said pin having a head, said polygonal portion being directly beneath said head.

11. A structure as described in claim 10 said body having a pair of spaced sides each provided with a polygonal recess therewithin, said handle being pivotally disposed between said sides, said polygonal portion upon said pin disposed within one of said polygonal recesses, a second polygonal member secured within the other of said polygonal recesses and provided with an opening adapted to accommodate said pin.

12. A rivet setting tool comprising, in combination, a body element of aluminum having a main portion and a substantially right-angled offset driving portion, a cylindrical slidably movable pulling member disposed within said driving portion, a plurality of jaws, within the pulling member, said main portion having a pair of spaced sides each provided with a polygonal opening therewithin and said driving portion being tubular and open at both ends, an insert of mild carbon steel having a knurled outer portion and a threaded inner portion secured within the threaded portion of said insert, sec- 0nd jaw spreading means coacting with the other end of said jaws, a coil spring one end of which abuts said second jaw spreading means disposed with said pulling member, a plug at one end of said pulling member abutting the other end of said spring, an elongated handle having an actuating portion disposed adjacent said pulling member, said coil spring adapted to bias said handle and the jaws into closed position, a pin connectiug said handle to said body element, said pin having an enlarged head and a polygonal portion therebeneath adapted to fit within one of the polygonal openings within said body, a polygonal holding element provided with an opening therewithin disposed within said other polygonal recess within said body, said pin passing through said opening within said holding element, said pin being thus retained against rotational movement, retaining means upon one end of said pin, a first boss upon one side of said body element adjacent the head I of said pin lying substantially flush with the projecting portion of said head, a second boss upon the opposite side of said body element lying substantially flush with the respective end of said pin, and a laterally projecting thumb rest element having a knurled face portion thereupon disposed upon the main portion of said body element beneath said handle. 

1. In a rivet setting tool having a body, selectively operable actuating means, support means for pivotally mounting the actuating means on the body and rivet setting means within the body responsive to pivotal movement of the actuating means, the improvement wherein said support means comprises: a. a pin-like element; and b. a member supporting the pin, said member having a polygonalshaped bearing surface; and c. a polygonal-shaped surface carried by the body disposed in substantially surface-to-surface mating relationship with respect to said first mentioned polygonal shaped surface.
 2. A rivet setting tool for blind rivets comprising, in combination, a body element having a main portion and aN offset driving portion, a plurality of co-acting jaws disposed within said offset driving portion, actuating means controlling said jaws, an elongated handle pivotally connected to said body portion and operatively connected to said actuating means, a pin having a pair of end portions passing through said elongated handle and said body element, a boss carried by said body element adjacent each of the end portions of said pin, said pin having an enlarged head element and a square holding portion beneath said head, the portion of said body element adjacent said square holding portion provided with a matching square opening for receiving said holding portion.
 3. A rivet setting tool as described in claim 2 wherein said body element is provided with an additional square opening laterally opposite said first named square opening and wherein a square holding element with a hole therethrough is disposed within said additional square opening.
 4. A rivet setting tool as described in claim 3 wherein the portion of said pin adjacent said square holding element has retaining means thereupon.
 5. A rivet setting tool as described in claim 4 wherein said retaining means comprises a washer member and a C-ring.
 6. In a rivet setting tool for blind rivets having a body formed with a hollow driving portion made of a soft metal, a pair of co-acting jaws within said driving portion and a bored nose piece for receiving the mandrel disposed within a hole in said driving portion adjacent said jaws, the improvement which comprises a tubular insert of a hard metal disposed within said hole in intervening relationship to said nose piece and said driving portion.
 7. A structure as described in claim 6 wherein said insert is made of mild carbon steel and said driving portion is made of aluminum.
 8. A structure as described in claim 7 wherein the portion of said nose piece within said hole is externally threaded and wherein said insert has an outer surface and an inner surface with knurling upon said outer surface and threads on said inner surface.
 9. In a rivet setting tool having a body, a handle member pivotally connected to said body, and rivet setting means operatively connected with said handle member, the improvement that comprises a pin pivotally connecting said handle member to said body, said pin having a polygonal portion disposed thereupon, said body having a mating polygonal recess to accommodate said pin so that said pin will not turn during pivotal movement of said handle.
 10. A structure as described in claim 9 said pin having a head, said polygonal portion being directly beneath said head.
 11. A structure as described in claim 10 said body having a pair of spaced sides each provided with a polygonal recess therewithin, said handle being pivotally disposed between said sides, said polygonal portion upon said pin disposed within one of said polygonal recesses, a second polygonal member secured within the other of said polygonal recesses and provided with an opening adapted to accommodate said pin.
 12. A rivet setting tool comprising, in combination, a body element of aluminum having a main portion and a substantially right-angled offset driving portion, a cylindrical slidably movable pulling member disposed within said driving portion, a plurality of jaws, within the pulling member, said main portion having a pair of spaced sides each provided with a polygonal opening therewithin and said driving portion being tubular and open at both ends, an insert of mild carbon steel having a knurled outer portion and a threaded inner portion secured within one end of said driving portion, a removable nose piece having first jaw spreading means thereupon coacting with one end of the jaws, said nose piece having a hole therewithin and being threadedly secured within the threaded portion of said insert, second jaw spreading means coacting with the other end of said jaws, a coil spring one end of which abuts said second jaw spreading means dispOsed with said pulling member, a plug at one end of said pulling member abutting the other end of said spring, an elongated handle having an actuating portion disposed adjacent said pulling member, said coil spring adapted to bias said handle and the jaws into closed position, a pin connecting said handle to said body element, said pin having an enlarged head and a polygonal portion therebeneath adapted to fit within one of the polygonal openings within said body, a polygonal holding element provided with an opening therewithin disposed within said other polygonal recess within said body, said pin passing through said opening within said holding element, said pin being thus retained against rotational movement, retaining means upon one end of said pin, a first boss upon one side of said body element adjacent the head of said pin lying substantially flush with the projecting portion of said head, a second boss upon the opposite side of said body element lying substantially flush with the respective end of said pin, and a laterally projecting thumb rest element having a knurled face portion thereupon disposed upon the main portion of said body element beneath said handle. 